Energy & Catalysis Session

Energy & Catalysis Session

Energy & Catalysis Session

Chair: Gil Shalev (BGU)

 

10:20-10:40

Avner Rothschild (Technion)
Keynote Speaker

Title:
Decoupled Water Splitting for Green Hydrogen Production at Scale

Abstract:
Green hydrogen produced by splitting water molecules into hydrogen and oxygen using renewable sources is expected to play a major role in the transition to carbon neutral economy, serving as an energy carrier that can facilitate the penetration of an higher share of intermittent renewable energy, the decarburization of hard-to-abate industrial sectors (e.g. industrial processes which require high-grade heating or rely on hydrogen as a feedstock) and the cross-sectorial coupling (linking power, gas and other energy vectors or energy intensive commodities and replacing them in their respective usages). The baseline technology for green hydrogen production is called water electrolysis, where renewable power is applied to break the chemical bonds in water molecules and produce hydrogen and oxygen simultaneously at two electrodes, cathode and anode, in alkaline or acidic solution. The coupled generation of hydrogen and oxygen at the same time in the same cell presents a safety risk, since the mixture of the two is highly flammable. Therefore, a membrane and sealing are used to isolate the electrodes from each other, which complicates cell construction and requires maintenance, both increasing the production cost of green hydrogen. In addition, severe (20-30%) energy losses, mostly due to the difficult reaction that evolves oxygen, increase the cost of energy in this energy intensive technology. These drawback present challenges for wide scale adoption of green hydrogen.
In order to overcome these challenges, we develop an alternative technology that decouples the generation of hydrogen and oxygen into two stages, separated by time, or two cells, space separated, avoiding the need for membrane and sealing. In addition, we divide the oxygen evolution reaction, a difficult electrochemical reaction that requires four electrons to generate an oxygen molecule on an atomic reaction site, into two sub-reactions that occur on four sites instead of one, thereby enabling easier reactions and saving most of the losses in water electrolysis. An ultrahigh efficiency of nearly 99% was demonstrated at lab scale, and we expect reaching 95% at system scale. To bring this transformative concept to reality we established H2Pro, and Israeli company that aims to provide green hydrogen at scale based on our innovation.

 

10:40-11:00

Nir Tessler (Technion)
Keynote Speaker

Title:
Device Synthesis applied to Organic Solar Cells

Abstract:
In the past 15 years, our group developed the methodology which we name “Device Synthesis.” The approach is based on the notion that it does not make sense to develop 3rd generation devices while forcing the materials to match the structure of the 1st generation devices. I will introduce the methodology in the context of device chemical-physics of organic solar cells. An example of the new approach is the realization that since organic molecules are not silicon, optimizing the maximum power point of a solar cell is not replaced by optimizing the short-circuit current and the open-circuit voltage. I will present two device structures designed with the above in mind.

 

11:00-11:15

Rafi Shikler (BGU)
Invited Speaker

Title:
On the effect of the finite conductivity and dielectric nature of ITO on the performance of organic based optoelectronic devices

Abstract:
Indium-Tin-Oxide (ITO) is one of the most commonly used materials for the fabrication of transparent electrodes for organic based optoelectronic devices. It is well known that its finite conductivity affects the scaling up of the area of organic solar cells. I will present a model that show how we use a 2D simulation to efficiently design a metal grid to overcome this issue. Another, rarely refer to, property of ITO is its relatively low dielectric constant. I will show that why it is important in the context of charge injection and collection into organic devices and present a modification to the commonly used Scott Malliaras model for contacts to organic materials.

 

11:15-11:30

Gideon Segev (TAU)
Invited Speaker

Title:
Operando characterization of charge extraction and recombination profiles in solar cells with nanoscale resolution

Abstract:
The next generation of solar energy conversion systems requires design and integration of new semiconductor materials. Detailed understanding of the opto-electronic properties of these materials, their driving forces and the loss mechanisms that limit device performance is essential to the development of high efficiency systems. However, these materials and systems are difficult to model and only few experimental methods are available for direct characterization of dominant loss processes under relevant operating conditions. To this end, empirical extraction of the spatial collection efficiency (SCE) and the spatial external luminescence efficiency (SELE) are operando, analytical tools that provide functional depth profiles of the active regions in the device.
By coupling external quantum efficiency (EQE) measurements and optical modeling, SCE extraction allows quantifying charge transport properties and loss mechanisms across the device depth profile under real operating conditions with very few assumptions. Similar to SCE, combining optical modeling with wavelength dependent photoluminescence quantum yield (PLQY) measurements enables extracting the SELE - the probability that an electron hole pair photogenerated at a specific point will contribute to photoluminescence from the device. In this contribution we will introduce the SELE concept and will show a first demonstration of the SELE extraction method applied to InP samples. Extracting the SELE enables simple distinction between different losses such as surface recombination and self-absorption. The quantification of surface recombination losses makes this an excellent tool for characterizing the effect of surface passivation layers. Furthermore, since the PLQY is directly related to the obtainable photovoltage from the device, the SELE also maps the contribution of different regions in the device to the photovoltage. As a result, combining the SELE and SCE profiles at specific operating points provides detailed spatial information on charge extraction, contribution to the photovoltage, and discrimination between radiative and non-radiative recombination processes at the surface and in the bulk of the device.

 

11:30-11:40

Igor Rahinov (OUI)
Contributed Speaker

Title:
The Kinetics of NH3 Desorption and Diffusion on Pt: Implications for the Ostwald Process

Abstract:
The Ostwald process is a critically important stepping-stone for industrial production of artificial fertilizers, converting ammonia (NH3) to nitric acid (HNO3) in the presence of oxygen and water. The key to its success is the efficient oxidation of NH3 to nitric oxide (NO) on a Pt catalyst. In industry the Ostwald process is conducted at temperatures of 1050-1250 K and total pressures between 1 and 12 bar with an ammonia to air ratio of 1:101. To initiate the oxidation, NH3 adsorbs with high probability to the majority terrace site and must then diffuse to low-coordination step-sites, where it is able to react with oxygen. Thus, the competition between desorption and diffusion and the equilibrium between adsorption at step and terrace-sites are critical factors in determining reaction probability; yet the competition between NH3 desorption and diffusion on Pt has never been investigated. There is not even an experimental consensus concerning such a basic parameter as the binding energy of NH3 at Pt(111). The lack of reliable quantitative information concerning NH3/Pt interactions led to surrogate empirically optimized models, which unfortunately lack universality and transferability.
In this work [1] we report accurate time-resolved measurements of NH3 desorption from Pt(111) and Pt(332) and use these results to determine elementary rate constants for desorption from steps, from (111) terrace sites and for diffusion on (111) terraces. Modeling the extracted rate constants with Transition State Theory (TST), we find that conventional models for partition functions, which rely on uncoupled degrees of freedom (DOFs), are not able to reproduce the experimental observations. The results can be reproduced by using a more sophisticated partition function, which couples DOFs that are most sensitive to NH3 translation parallel to the surface; this approach yields accurate values for the NH3 binding energy to Pt(111) (1.13±0.02 eV) and the diffusion barrier (0.71±0.04 eV). In addition we determine NH3’s binding energy preference for steps over terraces on Pt (1.23±0.03 eV). The ratio of the diffusion barrier to desorption energy is ~0.65, in violation of the so-called 12%-rule. Using our derived diffusion/desorption rates, we explain why established rate models of the Ostwald process incorrectly predict low selectivity and yields of NO under typical reactor operating conditions. Our results suggest that mean-field kinetics models have limited applicability for modelling the Ostwald process.
 
References
[1] J. Am. Chem. Soc. 2021, Published Online Ahead of Print, October 21, 2021; https://doi.org/10.1021/jacs.1c09269

 

11:40-11:50

Isaac Buchine (BIU)
Contributed Speaker

Title:
How does Humidity Affect Halide Perovskites’ Mechanical Properties?

Abstract:
ABX3 Halide Perovskites, HaPs, where A= Methylammonium (MA), Formamidinium (FA), or Cesium (Cs), B= Pb or Sn, X=Chloride (Cl), Bromide (Br), or Iodide (I), are promising materials for optoelectronics. Their intriguing optical and electronic properties, paired with their straightforward fabrication, make them outstanding candidates for incorporation into a variety of next generation technologies, as well as for exploring new material behavior.
The effect of humidity on HaP optoelectronic properties and degradation mechanisms has been thoroughly investigated, yet no studies exist on how it influences their structural and mechanical integrity, which is critical for their successful integration into future technologies. The humidity-dependent performance can also cast doubt on the generality of fundamental behavior, measured under uncontrolled humidity conditions.
Five different HaP single crystals, MAPbX3 (X = Cl, Br, and I) and APbBr3 (A = Cs and FA) were selected and grown to investigate the role that different A cations and X anions play for humidity-dependence of mechanical properties. A two-pronged approach employing both instrumented nanoindentation, and atomic force microscopy (AFM)-based nanomechanical measurements, was used to measure in situ changes in elastic and plastic deformation under different humidity conditions. AFM measurements included both elastic modulus determination using a contact resonance technique and hardness measurements using a diamond AFM tip to indent the sample and measure the profile in situ using the same tip. Hardness and modulus values were also measured by continuous stiffness measurements via instrumented nanoindentation, using the Oliver & Pharr approach.
We find that for MAPbCl3, MAPbBr3, MAPbI3 and FAPbBr3 the elastic modulus (E) increases 3-10% while the hardness (H) decreases by as much as ~25%, when RH (relative humidity) increases from 10% to 60% and that these changes are reversible. the A-site cation is found to play a critical role in determining the mode of deformation. The hardness values measured for FAPbBr3 and MAPbI3 were humidity dependent in the AFM measurements but not in the NI measurements, which is explained by the somewhat different properties obtained from these two techniques. CsPbBr3 shows negligible humidity dependence within experimental uncertainty.
We will discuss how the interplay between HaP composition and structure (how densely is the unit cell volume “filled” by the HaP constituents), and absorbed H2O can explain these observations.

 

11:50-12:10

Roundtable Discussions

 

Energy challenges that we face today, the Israeli corner

 

Moderator: Doron Aurbach (BIU)
Panel members: Emanuel Peled (TAU)

 

 

12:10-12:20

 
 

Our Sponsors

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IVS-IPSTA 2021 - 39th Annual Conference
November 17, 2021 | ONLINE

Conference Organizing Team


Gilbert Daniel Nessim (IVS President, BIU) | Ilya Grinberg (BIU) | Haim Barak (BIU)

Tatyana Bendikov (WIS) | Elad Koren (Technion) | Muhammad Bashouti (BGU) 
Noa Lachman-Senesh (TAU) | Igal Kronhaus (Technion)
Sharon Waichman (NRCN, Rotem Industries)